While various accumulating devices have hitherto been proposed which may be operated with an intermittent input and continuous output, such devices are relatively complex and generally comprise one of two kinds of prior art strip accumulators.
The first type of accumulating device is exemplified in U.S. Pat. No. 3,258,212, issued June 28, 1966 to Harry LaTour. According to the method disclosed in this patent, the strip is stored in a coil having a constant number of convolutions. When the supply to the coil is interrupted, the rotating table is stopped, but the strip continues to be paid off from the inside of the coil which is in an expanded condition, i.e., spaced outwardly from the roll cage. As this paying off continues, the convolutions collapse inwardly against the roll cage. The action of the storage coil is in effect a cyclic tightening and loosening without a change in the number of turns in the coil. One obvious disadvantage of this method is the relative scraping movement between adjacent convolutions which can produce unacceptable scratches of the surface of the strip material.
The second type of prior art "looping" accumulator is described in U.S. Pat. No. 3,310,255, issued Mar. 21, 1967 to Tadeusz Sendzimir. The device described in this patent stores the strip in two coaxial spiral coils, one of them being wound clockwise and the other counter-clockwise, with their inner portions being joined by a transition curve to form a continuous strip length.
Other prior art patents of interest include U.S. Pat. Nos. 3,506,210, issued Apr. 14, 1970 to Harry LaTour; 3,885,748, issued May 27, 1975 to Anthony C. Costello et al; 3,806,056, issued Apr. 23, 1974 to Harry LaTour; 3,265,321, issued Aug. 9, 1966 to R. Rahn; and 4,288,042 issued Sept. 8, 1981 to Tadeusz Sendzimir.
These patents are mentioned as being representative of the prior art and other pertinent references may exist. None of the above cited patents are deemed to affect the patentability of the present claimed invention.
In contrast to the prior art, the present invention provides a method and apparatus for transient storing of large quantities of longitudinally advancing elongated articles such as metallic and other strip, the storage being in a single spiral coil, subsequently referred to as "accumulator coil." Said coil, having a variable number of convolutions and a variable inner and outer diameter, has means to assure that the entry and exit speeds are independently controllable, even when one of them is zero. A typical application is for feeding processing lines, such as, pickling, chromium plating, annealing, etc., which all demand that strip be fed at a uniform uninterrupted velocity. Any stoppage or even slowing down of such lines, especially the modern fast ones, causes substantial losses in material that must be scrapped and in down-time for clearing and re-starting. Since such strip is available in coils, even though some weigh twenty tons or more, periodic stoppage at the entry end of said accumulator coil for butt-welding the leading end of the next supply coil to the tail end of previous supply coil to form a continuous web, are inevitable.
The present invention represents considerable advantages over the prior art. The accumulator coil can be completely emptied so there is no need to buy a machine of larger capacity than the actual stored length required; it is also more simple because there is no need for delicate controls of velocities between the coils and the transition curve.